Naegleria Infection (cont.)

N. fowleri is a water-borne disease. Exposure occurs when people come into contact with warm, fresh water usually through swimming, diving, water skiing, or other recreational activity. Although contact with infected water is common, symptomatic disease caused by N. fowleri is rare. It is common for people in the southern U.S. to have antibodies showing evidence of past exposure even when they have no history of symptoms or disease.

The danger of serious infection comes when water containing Naegleria fowleri is forced in into the nose and nasal mucosa. The parasite then migrates through the olfactory nerves and enters the brain. The initial step of infection can occur when diving or inadvertently aspirating water during swimming. Rarely, under-chlorinated swimming pools have been implicated in transmission. Because Naegleria fowleri can be present in untreated well water, there is a small but real chance of transmission to young children during bathing. Naegleria fowleri has also caused disease in adults who inject water into the nose as part of ritual ablutions related to religious practices.

The major risk factor for infection is recreational exposure to warm fresh water, especially if there is a history of aspiration of water into the nose. A review of cases in the U.S. by Yoder, et al. showed that there were 111 reported cases of primary amoebic encephalitis between 1962 and 2008. Living in the southern States is a risk factor for infection, because the water is warmer and more conducive to growth of the amoeba. A frequently asked question is when infections most commonly occur. The answer is that the organism is most active in summer months, even in the southern states. Most cases occur in previously healthy young males (median age of 12 years).

Source: MedicineNet.com
http://www.medicinenet.com/naegleria_infection/article.htm